The movement is unaffected by exposure to strong magnetic fields, even those greater than 1.5 tesla (15,000 gauss).
Label given to a watch which has undergone precision tests and received a certificate from an official body (COSC).
The day of the month, displayed in a window on a watch dial typically at the 3 o'clock or 6 o'clock position.
Helium escape valve
Decompression system which allows helium to escape from inside the watch when the watch is worn for professional use in pressure chambers. (Long‑term underwater work, crude oil exploration, etc.)
Self‑locking crown, screwed into the tube of the case, used for highly water resistant divers' watches.
Transparent case back
A transparent case back ‑ frequently made of sapphire ‑ makes it possible to see the movement inside the watch.
Unidirectional rotating bezel
A bezel which turns in only one direction. Particularly useful for divers who cannot accidentally rotate it in the wrong direction, which could cause them to miscalculate their dive times. A rotating bezel makes it easy to measure elapsed time.
Between lugs:20 mm
Case diameter:42 mm
Crystal:Domed scratch‑resistant sapphire crystal with anti‑reflective treatment on both sides